In the Thin Film Transistor Liquid Crystal Display (TFT-LCD) product, the FFS technology can increase an aperture ratio and transmittance of a liquid crystal display device with an In-Plane-Switching (IPS) mode.
A liquid crystal display device with an FFS mode includes a common electrode and a pixel electrode, which are separated by an insulation layer and arranged overlapped, and a distance between the common electrode and the pixel electrode is controlled to be less than a distance between an upper glass substrate and a lower glass substrate, so as to form a fringe field between the common electrode and the pixel electrode, so that liquid crystal molecules above the pixel electrode can be controlled, and the defect that the liquid crystal molecules are uncontrollable due to the vertical electric field right above the pixel electrode in the traditional IPS liquid crystal display device can be overcome, thereby increasing the aperture ratio and the transmittance of the liquid crystal display device greatly.
FIG. 1a is a schematic top view of a pixel unit of a liquid crystal display device with the FFS mode in the prior art. FIG. 1b is a schematic sectional view of the pixel unit of the liquid crystal display device with the FFS mode along a line A-A′ in FIG. 1a in the prior art. As shown in FIGS. 1a and 1b, a pixel unit 10 includes a pectinate pixel electrode 11, a planar common electrode 12, and an insulation layer 13 disposed between the pectinate pixel electrode 11 and the planar common electrode 12. The pixel electrode 11 includes a plurality of branch electrodes 111 arranged in parallel and end electrodes 112 connecting to ends of the branch electrodes 111, where, the lower end electrode is used to connect the pixel electrode to a switching device. After a voltage is applied between the pixel electrode 11 and the common electrode 12, an electric field component EY is formed by the end electrodes 112 and the common electrode 12 in a Y direction (i.e. a direction in which the branch electrodes extend). The existence of such electric field component causes the arrangement instability of the liquid crystal molecules at the edge of the pixel unit, in particularly, the electric field component in the Y direction affects a rotation direction of the liquid crystal molecules in a X-Y plane, thereby causing a Disclination Lines (DLS) phenomenon.
FIG. 2 is a schematic top view of a pixel unit of another existing liquid crystal display device with the FFS mode in the prior art. As shown in FIG. 2, a pixel unit includes a pixel electrode 21 and a common electrode 22 which are insulated with each other. The pixel electrode 21 includes branch electrodes 211 and end electrodes 212, where the lower end electrode is used to connect the pixel electrode to a switching device. The branch electrode includes a body 211a, and an inclined connection part 211b connected between an end of the body 211a and the end electrode 212, and the extension direction of the inclined connection part 211b is different from that of the body 211a, thereby forming an angle between the inclined connection part 211b and the body 211a. Due to the existence of the inclined connection part 211b at an end of the branch electrode 21, the electric field component EY formed by the end electrode 112 and the common electrode 12 in the Y direction (i.e. the extension direction of the strip electrode) can be reduced in a certain degree, to suppress the DLS phenomenon at the end of the pixel unit. The suppression of the DLS phenomenon by the pixel unit can be adjusted by adjusting the angle between the body 211a and the inclined connection part 211b as well as a length of the inclined connection part 211b during a design stage. However, the suppression of the DLS phenomenon by the pixel unit in such structure is still limited, and the display performance of an array substrate is significantly affected due to a poor press present in a central region of a pixel when the pixel is pressed.